High purity helium group gases are becoming increasingly important in various industrial processes. The improvement in the purity level of the helium group gases has increased their application in many industrial fields including welding, cryogenics, leak detection, semiconductor manufacturing, superconducting, etc. These gases are generally recovered as a byproduct during the separation of air to produce oxygen and nitrogen. Much of helium, however, is extracted from natural gas by successive liquification and purification.
Once the gases are concentrated or purified, they are usually transported to the use point via supply pipelines, gas cylinders or storage containers on rail cars or tractor trailers. During the transmission, however, the gases may be contaminated with oxygen, hydrogen and/or moisture. The helium at a delivery location, for example, contains 1 ppm moisture but, by the time it reaches the use point, the helium may have as much as two to three ppm moisture. Presumably, the moisture is from ambient in-leakage and/or desorption of moisture from the metal that is used for constructing the supply pipelines, gas cylinders or storage containers. Replacing the metal to inhibit contamination, however, would not be economically feasible since the supply pipelines, for instance, are normally quite long.
To mitigate such a problem, the use of commercial dryers or purifiers has been considered. The commercially available dryers and purifiers are either disposable type units (getter type unit) or regenerable type units (combination of thermal/chemical swing, pressure swing or both). Installing these dryers or purifiers at the use point is found to be unsuitable due to their complexity, expansiveness and inefficiency. The problem with the commercial disposable type units, for instance, is the difficulty of insuring the removal of contaminants without the use of on line analytical equipment while the problem with the commercial regenerable type units is complexed equipment involving automatic switching valves, regeneration means and/or possibly computer controlling means, which are expansive and elaborate.
Therefore, there is a need to design a purifier or dryer system which is suitable for installation at the use point, i.e., where the high purity helium group gases are used to produce particular products, devices, etc. In other words, less complex purifiers or dryers, which are efficient, effective and inexpensive, are desirable.